I am a four time convicted felon. And I am currently on probation. No drug or violent or sex crimes. My daughters mother is addicted to prescription pain killers. I am wanting to get full custody of my daughter. Id that possible?

Possible, yes, most likely not very likely, but if the court feels your home would be better it is possible. So she has been arrested for her adiction ? She has a record of abuse of drugs.

What can you present that is valid evidence of this in court ?

No. She has never been in trouble. Well, she has 2 assault charges for beating up her ex. Misdemeaners. She keeps a prescription at all timed. To the courts, she looks like a great person. Volunteers for casa, adult education, wings of hope, etc.
Possible, yes, most likely not very likely, but if the court feels your home would be better it is possible. So she has been arrested for her adiction ? she has a record of abuse of drugs.

What can you present that is valid evidence of this in court ?